Ferrite sintered magnet, motor and generator

Abstract

A ferrite sintered magnet contains a main phase formed of ferrite having a hexagonal magnetoplumbite type crystalline structure; a first subphase containing La, Ca, and Fe, in which an atomic ratio of La is higher than that of the main phase, and the atomic ratio of La is higher than an atomic ratio of Ca; and a second subphase containing La, Ca, Si, B, and Fe, in which an atomic ratio of Ca is higher than an atomic ratio of La, an atomic ratio of B is higher than an atomic ratio of Fe, and the atomic ratio of Fe is lower than that of the main phase. An area ratio of the second subphase on a cross-sectional surface of the ferrite sintered magnet is greater than or equal to 1%.

What is claimed is: 
     
       1. A ferrite sintered magnet, comprising:
 a main phase formed of ferrite having a hexagonal magnetoplumbite crystalline structure; 
 a first subphase containing La, Ca, and Fe, in which an atomic ratio of La is higher than that of the main phase, and the atomic ratio of La is higher than an atomic ratio of Ca; and 
 a second subphase containing La, Ca, Si, B, and Fe, in which an atomic ratio of Ca is higher than an atomic ratio of La, an atomic ratio of B is higher than an atomic ratio of Fe, and the atomic ratio of Fe is lower than that of the main phase, 
 wherein an area ratio of the second subphase on a cross-sectional surface, is greater than or equal to 9.9%, and 
 wherein the area ratio of the second subphase is larger than an area ratio of the first subphase, on the cross-sectional surface. 
 
     
     
       2. The ferrite sintered magnet according to  claim 1 ,
 wherein in the second subphase, when a total of La, Ca, Si, B, and Fe is set to 100 atom %, a ratio of La is 1 atom % to 25 atom %, a ratio of Ca is 30 atom % to 70 atom %, a ratio of Si is less than or equal to 50 atom %, a ratio of B is 8 atom % to 60 atom %, and a ratio of Fe is less than or equal to 20 atom %. 
 
     
     
       3. The ferrite sintered magnet according to  claim 1 , wherein the area ratio of the first subphase on the cross-sectional surface is less than or equal to 5%. 
     
     
       4. The ferrite sintered magnet according to  claim 1 , wherein the ferrite sintered magnet contains CaB 2 O 4 . 
     
     
       5. The ferrite sintered magnet according to  claim 2 , wherein the ferrite sintered magnet contains CaB 2 O 4 . 
     
     
       6. The ferrite sintered magnet according to  claim 3 , wherein the ferrite sintered magnet contains CaB 2 O 4 . 
     
     
       7. The ferrite sintered magnet according to  claim 4 , wherein the second subphase contains CaB 2 O 4 . 
     
     
       8. The ferrite sintered magnet according to  claim 5 , wherein the second subphase contains CaB 2 O 4 . 
     
     
       9. The ferrite sintered magnet according to  claim 6 , wherein the second subphase contains CaB 2 O 4 . 
     
     
       10. The ferrite sintered magnet according to  claim 4 , wherein an area ratio of CaB 2 O 4  contained in the second subphase, is less than or equal to 2%, on the cross-sectional surface. 
     
     
       11. The ferrite sintered magnet according to  claim 5 , wherein an area ratio of CaB 2 O 4  contained in the second subphase, is less than or equal to 2%, on the cross-sectional surface. 
     
     
       12. The ferrite sintered magnet according to  claim 6 , wherein an area ratio of CaB 2 O 4  contained in the second subphase, is less than or equal to 2%, on the cross-sectional surface. 
     
     
       13. A motor comprising:
 the ferrite sintered magnet according to  claim 1 . 
 
     
     
       14. A generator comprising:
 the ferrite sintered magnet according to  claim 1 . 
 
     
     
       15. A ferrite sintered magnet, comprising:
 a main phase formed of ferrite having a hexagonal magnetoplumbite crystalline structure; 
 a first subphase containing La, Ca, and Fe, in which an atomic ratio of La is higher than that of the main phase, and the atomic ratio of La is higher than an atomic ratio of Ca; and 
 a second subphase containing La, Ca, Si, B, and Fe, in which an atomic ratio of Ca is higher than an atomic ratio of La, an atomic ratio of B is higher than an atomic ratio of Fe, and the atomic ratio of Fe is lower than that of the main phase, 
 wherein an area ratio of the second subphase on a cross-sectional surface, is greater than or equal to 1%, and 
 wherein in the second subphase, when a total of La, Ca, Si, B, and Fe is set to 100 atom %, a ratio of La is1 atom % to 25 atom %, a ratio of Ca is 30 atom % to 70 atom %, a ratio of Si is less than or equal to 50 atom %, a ratio of B is 8 atom % to 60 atom %, and a ratio of Fe is less than or equal to 20 atom %. 
 
     
     
       16. The ferrite sintered magnet according to  claim 15 , wherein the ferrite sintered magnet contains CaB 2 O 4 . 
     
     
       17. The ferrite sintered magnet according to  claim 16 , wherein the second subphase contains CaB 2 O 4 . 
     
     
       18. The ferrite sintered magnet according to  claim 16 , wherein an area ratio of CaB 2 O 4  contained in the second subphase, is less than or equal to 2%, on the cross-sectional surface. 
     
     
       19. The ferrite sintered magnet according to  claim 15 , wherein the area ratio of the second subphase on the cross-sectional surface is greater than or equal to 9.9%. 
     
     
       20. A ferrite sintered magnet, comprising:
 a main phase formed of ferrite having a hexagonal magnetoplumbite crystalline structure; 
 a first subphase containing La, Ca, and Fe, in which an atomic ratio of La is higher than that of the main phase, and the atomic ratio of La is higher than an atomic ratio of Ca; and 
 a second subphase containing La, Ca, Si, B, and Fe, in which an atomic ratio of Ca is higher than an atomic ratio of La, an atomic ratio of B is higher than an atomic ratio of Fe, and the atomic ratio of Fe is lower than that of the main phase, 
 wherein an area ratio of the second subphase on a cross-sectional surface, is greater than or equal to 1%, 
 wherein the area ratio of the second subphase is larger than an area ratio of the first subphase, on the cross-sectional surface, 
 wherein the ferrite sintered magnet contains CaB 2 O 4 , and 
 wherein an area ratio of CaB 2 O 4  contained in the second subphase, is less than or equal to 2%, on the cross-sectional surface.